Printing devices that print images by forming dots on a print medium are in widespread use. Some such printing devices employ an interlaced printing method known in the art in which dots are formed on adjacent main scanning lines in different main scans. Using interlaced printing, a printing device can print at a higher resolution, whereby the pitch of dots in the sub-scanning direction (the line spacing of adjacent main scanning lines) is smaller than the nozzle pitch in the sub-scanning direction.
A printer possessing a printing technology known in the art prints a prescribed pattern having a plurality of main scan lines that include a reference main scan line, measures the amounts of offsets between the reference main scan line and the non-reference main scan lines in the printed pattern, and calibrates a conveyance control amount for conveying the paper based on the measured offset. This technology calibrates the conveyance control amount so that the actual paper-conveying distance is adjusted to the ideal conveying distance for each of various printing modes that differ according to their method of interlaced printing.